Regulators need to study 20 natural gas disposal pits to determine if a link exists between Pavillion's gas field and the area's contaminated drinking water, according to a draft report by the Wyoming Oil and Gas Conservation Commission. The study, one of three undertaken by the state concerning Pavillion's groundwater, offered no firm conclusions to the question that has long bedeviled the small central Wyoming community, namely what is responsible for the area's poor drinking water.
It did, however, outline steps the state and the field's operator, Encana Corp., need to take to determine whether a series of pits are potential sources of contamination.
"The report is one step in the process here," said Tom Kropatsch, deputy oil and gas supervisor and one of the report's authors.
Public comment on the draft will be open until Jan. 16. Beyond that date, there is no firm timeline for finalizing the report and implementing the recommendations, he said.
The 20 pits identified for further study represent a fraction of the total number of disposal sites in the Pavillion field. All were within a quarter-mile of a drinking water well.
Disposal pits are used to store drilling waste, which can include anything from the fluids injected into a well to the rock removed from it. The Pavillion field has 92 disposal pits and 169 natural gas wells, the report said.
The pits themselves can be classified into two broad categories: older pits used to store liquids used in the drilling process and newer ones for dried rock, or cuttings, removed from the well. The report stated 12 pits storing oil-based mud used in drilling had been studied but needed further examination. More analysis will help determine the pits' contents and whether any cleanup is needed. Seven unstudied pits storing oil-based mud also require more investigation to determine whether any potential pathways between disposal sites and drinking water wells exist, it said.
And samples are needed from one of nine pits containing potassium chloride, the report said. Wells drilled with water-based mud sometimes used potassium chloride, which could potentially pollute drinking water, the study stated. The draft recommended samples be taken from one pit located within 100 feet of a water well. That drinking source, the report noted, presented the greatest chance for contamination.
However, more work is needed to determine the exact location and depth of that water well, the report said. A State Engineer's Office permit, which would put the well near the pit, stated its depth was about 90 feet. EPA figures put the same well's depth around 500 feet.
More information about the general hydrology of the Pavillion field is also needed to decide if a link between natural gas operations and drinking water pollution exists, the report stated. There's no agreement over why Pavillion's drinking water is contaminated. Some have argued natural gas wells are to blame for the polluted water. Others have said some combination of naturally occurring contamination and deep water wells are responsible.
A draft U.S. Environmental Protection Agency report linked the faulty water to natural gas operations in the area, but the agency ultimately handed over its investigation to Wyoming after the report's findings provoked a fierce uproar from industry and state officials.
Encana is reviewing the Wyoming draft report, said Doug Hock, a company spokesman. The Canadian-based firm plans to submits comments to the state once it finishes the review, he said.
Jill Morrison, an organizer at the Powder River Basin Resource Council, a landowners group, said the proximity of water wells to pits identified for further review is a concern. She sought to tie the report's findings to the ongoing debate over greater buffers between oil and gas development and dwellings. The current setback is 350 feet. A state proposal would increase the distance to 500 feet. The resource council has proposed a distance of a quarter mile.
"The bigger picture, in terms of what can we do in the future, is to prevent a Pavillion-type of situation. And what keeps coming back repeatedly is oil and gas development is an industrial activity that leads to greater contamination," Morrison said. "In Pavillion, they’re looking at a quarter-mile contamination for water wells."
The draft released last week is the second preliminary report completed by the Wyoming Oil and Gas Conservation Commission. The first, released in August, examined the integrity of gas wells in the Pavillion field. A third study into groundwater quality is being conducted by the state Department of Environmental Quality.
